Simplified electromechanical oscillator

ABSTRACT

Permanent magnet mounted on an oscillatory arm controlled by a hairspring swings past a stationary coil having oppositely wound sensing and driving portions. Voltage induced in the sense coil by movement of the magnet triggers a transistor; pulses of current caused thereby to flow in the collector-emitter circuit of the transistor pass through the driving portion of the coil. With the coil connections shown the action is regenerative, running the transistor to saturation. The field of the drive coil imparts a mechanical force to the magnet, and maintains it in oscillatory movement.

United States Patent Inventor Frank II. Marz Delavan, Wis.

Appl. No. 18,678

Filed Mar. 11, 1970 Patented Oct. 12, 1971 Assignee The Bunker-Ramo Corporation Oak Brook, Ill.

Continuation-impart of application Ser. No. 831,046, m .3 96 Q1E FEFQPSQ:

SIMPLIFIED ELECTROMECHANICAL OSCILLATOR 6 Claims, 7 Drawing Figs.

U.S. Cl 318/128, 318/132, 58/23 Int. Cl 02k 33/00 Field of Search .318/119-135;

58/213,28; 31mm, 116 M References Cited UNITED STATES PATENTS 3,100,278 8/1963 Reich 318/132 X 3,149,274 9/1964 l-letzel 318/132 X 3,359,473 12/1967 Negri 318/132 X Primary Examiner-D. F. Duggan Attorney-Frederick M. Arbuckle ABSTRACT: Permanent magnet mounted on an oscillatory arm controlled by a hairspring swings past a stationary coil having oppositely wound sensing and driving portions. Voltage induced in the sense coil by movement of the magnet triggers a transistor; pulses of current caused thereby to flow in the collector-emitter circuit of the transistor pass through the driving portion of the coil. With the coil connections shown the action is regenerative, running the transistor to saturation. The field of the drive coil imparts a mechanical force to the magnet, and maintains it in oscillatory movement.

PAlENTEflncnzlsn 3,612,968

f i saw 10F 2 IN VE N TOR Frank H. Marz 1 SIMPLIFIED ELECTROMECIIANICAL OSCILLATOR RELATED APPLICATIONS BACKGROUND OF THE INVENTION The present invention relates generally to electromechanical oscillators used, for example, as the timing mechanism in clocks or watches, and further relates particularly to an economical, simplified oscillating structure and associated circuitry requiring a minimum of components and a minimum of electrical energy for operation.

The need exists for an electromechanical oscillating device having simple magnetic and mechanical structures and low power requirements such as would adapt it for use with a battery as a source of energy. Many of the electromechanical oscillators presently known and available employ permanent magnets with their poles in operative relation with a plurality of coil structures, and in some cases the coil structures have iron cores. With such devices the power requirementsare often quite substantial, and in devices requiring a plurality of coils there is obviously an additional manufacturing cost involved for each coil.

Further, the existing art shows many instances of the usage of a transistor as a switching device, triggered by a voltage induced in a sensing coil by the movement of a magnet relative thereto. However, the normal use of a transistor involves a power loss in the transistor itself, which does not contribute to maintaining the energy in the mechanical system. Where a timepiece is operated on battery power, this may unduly limit the useful life of the battery.

BRIEF SUMMARY OF THE INVENTION The present. invention provides a single permanent magnet mounted for oscillatory movement past a single, stationary coil having oppositely wound sensing and drive portions. A single low-voltage switching device, such as a transistor, is connected to the coil. Movement of the magnet is effective to induce a voltage in the sensing portion of the coil. When this voltage is of appropriate polarity and magnitude, it is sufficient to switch the transistor to an on" condition, the transistor then being effective to pass current, through the drive portion of the coil. The arrangements of the coils and their connections to the transistor are such that this action is regenerative, and during the conducting period a highfrequency cyclic voltage is applied to the coil. The field of the coil reacts with that of the magnet to add energy to the mechanical oscillating system and maintain it in continued operation.

The regenerative feature arises from the fact that the two portions of the coil are wound in opposite directions. It has the effect that, when the transistor is triggered, it goes to saturation. Since the internal resistance of the transistor is low in this condition, energy loss in the transistor is minimized, and battery life is thereby extended.

THE DRAWING The invention with its advantages and objectives, will be more apparent from consideration of the following detailed description taken in connection with the accompanying drawings in which:

FIG. I shows a diagrammatic representation of an electromechanical oscillator constructed in accordance with the FIG. 4 is a graphical representation of the EMF induced in the sense coil by the changing fluxIofFIG. 3. 1

FIGJS is adiagrammatic representation corresponding in time scale toth'e iother figures, showing the current flowing in ve wil FIG. '6 represents a portion of FIG. 5, on an expanded time scale.

FIG. 7 is a diagrammatic representation of the electromagnetic elements of the oscillator.

DETAILED DESCRIPTION FIG. 1 shows diagrammatically an embodiment of the invention comprising a switching circuit 1 and a mechanically oscillating structure 2, the circuit and structure forming an electromechanical oscillator 3 in accordance with the principles of the invention as hereinafter explained.

The circuit 1 is comprised essentially of four components, namely, a transistor 4, a unitary stationary coil 6 having an air or nonferrous core, a direct current supply means or power source 8, and impedance means, such as a resistor 10, connected across a portion of the coil. The base terminal of the transistor is electrically connected to one end of the coil while the positive side of the power source is connected to the other end of the coil. The emitter of the transistor is electrically connected to a tap 12 of the coil, the tap dividing the coil into a sensing portion 14 and a drive portion 16. The collector is connected to the negative side of the power source.

The power source may be any voltage provided by batteries, typically 1.5 volts, and the transistor 4 may be a PNP- or NPN- type germanium or silicon switching transistor; for example, a 2N2953, though other switching devices may be used.

In a preferred embodiment of the invention, the drive portion 16 of the coil 6 comprises approximately 1,200 turns of number 44 copper wire, and the sensing portion 14 is formed by approximately 4,000 turns of number 44 copper wire,--the turns of the sensing portion being wound in the direction opposite to that of the drive portion, as shown in FIG. I. For the resistor 10, a value of approximately 7,000 ohms has been found to provide a suitable on time period for the transistor 4 in the embodiment of the invention here described.

The mechanical structure 2 includes a small, cylindrical permanent magnet 18 eccentrically supported in a plate or balance wheel 20 made of a nonmagnetic material. The wheel is keyed or otherwise fixed to a balance staff or spindle 22, the ends of which are mounted for rotational movement about the axis of the spindle in bearing means not shown.

To balance the weight of the magnet 18, a nonferrous counterweight 24 is located on the plate 20 in a position diametrically opposite to that of the magnet.

A hairspring 26 is connected between the staff 22 and a fixed surface 28 for mechanically biasing the balance wheel 20 and staff 22. The spring is adjusted so that in the rest position the axis of the magnet 18 is slightly displaced from that of the coil 6. The staff may be provided with a ladder escapement 30 for driving a conventional gear train (not shown) as used in timing and metering devices.

Operation of the system is initially described most easily in terms of the events occurring during normal sustained operation.

FIG. 2 illustrates the arcuate path through which the magnet travels in the movement of the balance wheel 20. In its passage from the position shown in full lines in FIG. 2 to the position shown in dotted outline the magnet swings across the coil 6. In actual practice the total are of oscillation may be considerably greater than that shown in FIG. 2, but the illustration is adequate for purposes of explanation. Whatever the position of the magnet, it will be creating a magnetic field through the coil, and the magnitude and direction of the flux so created is graphically represented in FIG. 3. The central axis in the diagram of FIG. 3 corresponds to the axis of coil 6, and distances to the left and right thereof correspond to similar distances in FIG. 2. The vertical dimension indicates relative value of magnetic flux through the coil, when the magnet is at a particular abscissa position.

The varying flux diagrammed in FIG. 3 will induce in the sense coil 14 an EMF proportional to the rate of change of the flux. The magnitude and polarity of this EMF are diagrammed in the solid lines of FIG. 4. This EMF is effective between the emitter and base of the transistor 4 and when it is of sufficient magnitude and in proper polarity it will cause the transistor to become conductive. The strong voltage pulse which occurs just after the magnet has passed the center line of the coil in a movement from left to right in FIG. 2 is shown just to the right of the center line in FIG. 4. It causes the transistor to become conductive, and current flows in the drive coil 16 under the influence of the power source 8. Once the transistor has begun to conduct the effect is regenerative and may be explained by reference to FIG. 7.

FIG. 7 shows a south pole of the magnet adjacent to the drive coil 16. The field of the magnet is illustrated by the dotted lines and the direction of the field is indicated by the arrow 40. The triggering voltage shown in FIG. 4 is the result of the decrease in field strength shown in FIG. 3 after the magnet has passed the center line of the coil. Referring now to FIG. 7, a decreasing field in the direction indicated by the arrow will induce an EMF in the sense coil 14 tending to cause a flow of current in the direction indicated by the arrow 42. This EMF is the one shown in FIG. 4, just to the right of the center axis. It renders the emitter positive with respect to the base, and causes current to flow in the collector-emitter loop. The latter current flows in the direction indicated by the arrow 44, which produces a field in the drive coil 16 in the direction opposite to the arrow 40. The effect of this is to further the decrease in the field which produced the original trigger EMF. The tendency, therefore, is to increase the trigger EMF and to run the transistor to saturation very rapidly.

The circuit is not oscillatory in its normal condition, but the coupling between the sense and drive coils varies with the position of the magnet. The magnet in its movement, in effect, varies the permeability of a part of the field of those coils and hence changes the field linking both coils. The magnitude of this effect on the degree of coupling is suggested by the dotted line 46 in FIG. 4. During the period in which the transistor is conductive, oscillation does take place, with the result indicated in FIG. 5. On an expanded time scale a single pulse of the oscillation is shown in FIG. 6. From this it will be seen that the net conduction is very strongly unidirectional and that it nearly all takes place at the saturation current limit of the transistor.

With'the current flowing in the direction indicated by the arrow 44, the top face of the coil 16 becomes a south pole and repels the south pole of the magnet, thus contributing a pulse of energy to the mechanical oscillating system sufficient to maintain it in operation. As soon as the induced EMF in the sense coil circuit drops to a low level the electrical oscillation ceases and the transistor returns to its quiescent nonconductive state.

The mechanism can be started by physically displacing the balance wheel from its position of rest, or by electrical means in the switching circuit. Perhaps the simplest device for the latter purpose is a momentary contact switch 48 connected between collector and emitter of the transistor as shown in FIG. 7. Brief closure of this switch will pass current from the power supply 8 through the drive coil 16, setting up a field which will repel the magnet S and start the balance wheel 20 in motion. a

The oscillator system described herein has remarkable ad vantages from the standpoint of economy in'the use of power from the source 8. This is due mainly to the regenerative character of the circuit, whereby nearly all the current which flows from the power source does so with the transistor at saturation point. This is the condition where the losses in the transistor are at a minimum. The result is very long battery life in uses where a dry cell is employed as a power source.

The system is also economical to manufacture by reason of the unitary coil, which means only a single part to be handled and provided with a mounting, whereas older devices have two or more coils, separately mounted.

Since the regenerative and oscillatory nature of the switching circuit is due to the arrangement of the windings in the coil, it is important to make the proper relation clear. The winding sense is illustrated in FIG. 1 and 7, and has been described above in terms that the coils are wound in opposite directions. This language is correct if the two portions of the coil be regarded from either end terminal. If winding were started, for example, from the upper end of the coil 6 in FIG. I, the direction of winding must be reversed when the tap 12 is reached. On the other hand, one economical way of winding the coil to obtain the sameresult is to start, in effect, from the tap or common terminal 12, winding two wires simultaneously, in the same direction, bringing out each end terminal at the proper number of turns.

Although the invention has been described with a certain degree of particularity, some changes may be made therein without departing from the spirit and scope thereof. The foregoing description is only illustrative of the specific forms which the invention may take. It is intended therefore that the detailed description be considered as exemplary only, and that the scope of the invention be ascertained from the following claims.

That which is claimed is:

1. In an electromechanical oscillator having a permanent magnet mounted for oscillatory movement and spring means biasing the movement of said magnet toward a neutral position, the improvement consisting of a unitary stationary coil having oppositely wound sensing and drive coil portions coaxially positioned about a nonferrous core, and mounted to be passed by said magnet in closely adjacent relation near the point of neutral bias of said spring means, a current supply means, and transistor switching means having a collector connected via said current supply to one terminal of the drive portion of said coil, a base connected to one terminal of the sensing portion of said coil, an emitter connected tothe junction of the drive and sensing portions of said coil, and starting means including a switch permitting momentary connection between the collector and emitter.

2. In an electromechanical oscillator having a permanent magnet mounted for oscillatory movement and spring means biasing the movement of said magnet toward a neutral position, the improvement consisting of a unitary stationary coil having oppositely wound sensing and drive coil portions coaxially positioned about a nonferrous core, and mounted to be passed by said magnet in closely adjacent relation near the point of neutral bias of said spring means, a current supply means, and transistor switching means having a collector connected via said current supply to one terminal of the drive portion of said coil, a base connected to one terminal of the sensing portion of said coil, an emitter connected to the junction of the drive and sensing portions of said coil, and a resistance connected between the base and emitter.

3. In an electromechanical oscillator having a permanent magnet mounted for oscillatory movement and spring means biasing the movement of said magnet toward a neutral position, the improvement consisting of a unitary stationary coil having oppositely wound sensing and drive coil portions coaxially positioned about a nonferrous core, a current supply means, and a transistor having a collector connected via said current supply to one terminal of the drive portion of said coil, a base connected to one terminal of the sensing portion of said coil, and an emitter connected to the junction of the drive and sensing portions of the coil, said coil being mounted to be passed by said magnet near the point of neutral bias of said spring means, sufficiently closely to render the circuit oscillatory when the transistor is conductive, and starting means including a switch permitting momentary connection between the collector and emitter.

4. In an electromechanical oscillator having a permanent magnet mounted for oscillatory movement and spring means biasing the movement of said magnet toward a neutral position, the improvement consisting of a unitary stationary coil having oppositely wound sensing and drive coil portions coaxially positioned about a nonferrous core, a current supply means, and a transistor having a collector connected via said current supply to one terminal of the drive portion of said coil, a base connected to one terminal of the sensing portion of said coil, and an emitter connected to the junction of the drive and sensing portions of the coil, said coil being mounted to be passed by said magnet near the point of neutral bias of said spring means, sufficiently closely to render the circuit oscillatory when the transistor is conductive, and a resistance connected between the base and emitter.

5. In an electromechanical oscillator having a cylindrical pennanent magnet with poles substantially at opposite ends of the cylinder, mounted for oscillatory movement in a plane perpendicular to the axis of said cylinder, and spring means biasing the movement of said magnet toward a neutral position, the improvement consisting of a unitary stationary coil having sensing and drive coil portions coaxially positioned about a nonferrous core, said coil being mounted with its axis perpendicular to the plane of movement of said magnet and in position to be passed by said magnet in closely adjacent relation near the point of neutral bias of said spring means, the sensing and drive coil portions of said coil having a common junction, and being wound in the same direction with reference to and proceeding from said junction, and transistor switching means having an emitter connected to said junction, a base connected to the end terminal of the sensing portion of said coil, and a collector connected via a current supply means to the end terminal of the drive portion of said coil.

6. The invention in accordance with claim 5, and a resistor connected between the base and emitter. 

1. In an electromechanical oscillator having a permanent magnet mounted for oscillatory movement and spring means biasing the movement of said magnet toward a neutral position, the improvement consisting of a unitary stationary coil having oppositely wound sensing and drive coil portions coaxially positioned about a nonferrous core, and mounted to be passed by said magnet in closely adjacent relation near the point of neutral bias of said spring means, a current supply means, and transistor switching means having a collector connected via said current supply to one terminal of the drive portion of said coil, a base connected to one terminal of the sensing portion of said coil, an emitter connected to the junction of the drive and sensing portions of said coil, and starting means including a switch permitting momentary connection between the collector and emitter.
 2. In an electromechanical oscillator having a permanent magnet mounted for oscillatory movement and spring means biasing the movement of said magnet toward a neutral position, the improvement consisting of a unitary stationary coil having oppositely wound sensing and drive coil portions coaxially positioned about a nonferrous core, and mounted to be passed by said magnet in closely adjacent relation near tHe point of neutral bias of said spring means, a current supply means, and transistor switching means having a collector connected via said current supply to one terminal of the drive portion of said coil, a base connected to one terminal of the sensing portion of said coil, an emitter connected to the junction of the drive and sensing portions of said coil, and a resistance connected between the base and emitter.
 3. In an electromechanical oscillator having a permanent magnet mounted for oscillatory movement and spring means biasing the movement of said magnet toward a neutral position, the improvement consisting of a unitary stationary coil having oppositely wound sensing and drive coil portions coaxially positioned about a nonferrous core, a current supply means, and a transistor having a collector connected via said current supply to one terminal of the drive portion of said coil, a base connected to one terminal of the sensing portion of said coil, and an emitter connected to the junction of the drive and sensing portions of the coil, said coil being mounted to be passed by said magnet near the point of neutral bias of said spring means, sufficiently closely to render the circuit oscillatory when the transistor is conductive, and starting means including a switch permitting momentary connection between the collector and emitter.
 4. In an electromechanical oscillator having a permanent magnet mounted for oscillatory movement and spring means biasing the movement of said magnet toward a neutral position, the improvement consisting of a unitary stationary coil having oppositely wound sensing and drive coil portions coaxially positioned about a nonferrous core, a current supply means, and a transistor having a collector connected via said current supply to one terminal of the drive portion of said coil, a base connected to one terminal of the sensing portion of said coil, and an emitter connected to the junction of the drive and sensing portions of the coil, said coil being mounted to be passed by said magnet near the point of neutral bias of said spring means, sufficiently closely to render the circuit oscillatory when the transistor is conductive, and a resistance connected between the base and emitter.
 5. In an electromechanical oscillator having a cylindrical permanent magnet with poles substantially at opposite ends of the cylinder, mounted for oscillatory movement in a plane perpendicular to the axis of said cylinder, and spring means biasing the movement of said magnet toward a neutral position, the improvement consisting of a unitary stationary coil having sensing and drive coil portions coaxially positioned about a nonferrous core, said coil being mounted with its axis perpendicular to the plane of movement of said magnet and in position to be passed by said magnet in closely adjacent relation near the point of neutral bias of said spring means, the sensing and drive coil portions of said coil having a common junction, and being wound in the same direction with reference to and proceeding from said junction, and transistor switching means having an emitter connected to said junction, a base connected to the end terminal of the sensing portion of said coil, and a collector connected via a current supply means to the end terminal of the drive portion of said coil.
 6. The invention in accordance with claim 5, and a resistor connected between the base and emitter. 